An exhaust manifold, elongated along the bank of cylinders, which thus also receives the exhaust gases being discharged from the cylinders and is generally also called exhaust manifold, is fixed on an exhaust side of the cylinder head in internal combustion engines used in motor vehicles, which are configured, in general, as multicylinder internal combustion engines with at least one bank of cylinders formed in a cylinder block. The exhaust manifold has an essentially flat contact surface, which is supported in relation to a likewise essentially flat contact surface of the cylinder head via the intermediary of a sealing element. The exhaust manifold has respective fastening edge areas on its longitudinal sides. Fastening elements supported on the fastening edge areas by fastening bolt units fixed on the cylinder head by, for example, screw connection are pressed against the fastening edge areas and against respective fastening element support surfaces provided there and against the cylinder head, so that the exhaust manifold is pressed against the contact surface of the cylinder head, of course, via the intermediary of the aforementioned sealing element to establish a gastight closure.
It may be necessary for structural reasons not to arrange the fastening bolt units supported in relation to the cylinder head, on the one hand, and to a fastening element, on the other hand, at right angles to the contact surface of the at least one of the fastening edge areas, but inclined in relation thereto in order to have access to the fastening bolt units when fixing the exhaust manifold on the cylinder head. This inclined arrangement of the fastening bolt units on at least one of the fastening edge areas requires a wedge-like configuration of a fastening flange area, which is provided on this fastening edge area and on which the fastening element pressed by these fastening bolt units against the fastening edge area is supported. Lateral forces, which stress the exhaust manifold in the direction of its other fastening edge area as well as the fastening bolt units provided there and the fastening element provided there are generated due to this inclined arrangement of the fastening bolt units and the wedge-like configuration of the fastening flange area.
Just as the cylinder head, the exhaust manifold is subject to a high thermal load and high mechanical stress during the operation of an internal combustion engine. The heat-induced expansions and contractions occurring at the beginning of a combustion operation and after the end of a combustion operation repeatedly give rise to forces in the area of the fixing of the exhaust manifold on the cylinder head as well, and these forces also exert a great stress on the fastening bolt units used to fix the exhaust manifold on the cylinder head and, also supported by the vibrations occurring during the combustion operation, these forces may also lead to a loosening of fastening bolt units and to an installed position deviating from the desired installed position of the exhaust manifold in relation to the cylinder head.